1. Field of the Invention
The invention concerns a surface processing apparatus in which the surface of an object is subjected to plasma processing, and it concerns a plasma processing apparatus in which semiconductor elements are made by plasma processes such as dry etching, plasma enhanced chemical vapor deposition (PECVD) and sputtering.
2. Description of Related Art
The surfaces of objects are frequently processed using plasma when making semiconductor elements such as LSI (large integrated circuits) and flat panel displays such as LCD (liquid crystal displays).
Non-equilibrium plasma, the so-called low temperature plasma, is widely used as a means of effectively carrying out surface reactions with chemically active radicals while keeping the surface of the object at a low temperature. Systems in which plasma is generated using high frequencies have been adopted in the past as a means of generating such low temperature plasmas.
An apparatus in which microwaves were used was developed long ago as a type of surface processing apparatus in which plasma was generated using high frequencies. In this case, for imparting energy to the electrons, the method in which the frequency at which the electrons are made to undergo cyclotron motion by the action of a magnetic field is matched to a microwave frequency and a resonance state is achieved, and the method in which the microwaves are introduced into a cavity resonator and their amplitude is increased, have been used as methods of imparting energy to electrons.
Conventional apparatus of the latter type to which the invention of the present invention relates is described below.
The apparatus indicated in Japanese Unexamined Patent Application 56-96841 can be cited as an example of a surface processing apparatus in which a cavity resonator is used. A drawing of the conventional surface processing apparatus indicated in Japanese Unexamined Patent Application 56-96841 is shown in FIG. 8.
In the surface processing apparatus of this conventional apparatus, the microwaves generated in the microwave generator 1 are introduced into the cavity resonator 2 and resonate. The surface processing of the substrate 30 which has been mounted on the substrate mounting platform 31 inside the process chamber 3 is carried out by means of the plasma which has been generated thereby. The gas supply port 32 and the exhaust port 33 are established in the process chamber 3. Gas is introduced into the process chamber 3 and the abovementioned plasma is generated in this gaseous atmosphere.
With the conventional surface processing apparatus shown in FIG. 8, the plasma is generated in the cavity resonator 2 and so the resonance conditions of the cavity resonator 2 are inevitably changed by the effect of the plasma. Consequently there is a disadvantage in that the plasma is unstable.
Apparati of the type indicated below have been developed for resolving this problem, and these include those indicated in Japanese Unexamined Patent Application H8-246146 and in Japanese Examined Patent Publication H8-31444. As an example, a drawing of the conventional surface processing apparatus indicated in Japanese Examined Patent Publication H8-31444 is shown in FIG. 9.
In the surface processing apparatus shown in FIG. 9, a dielectric plate 41 is established between the cavity resonator 2 and the process chamber 3 for dividing the cavity resonator 2 and the process chamber 3.
A chamber flange 34 is established as shown in FIG. 9 on an edge of the upper opening of the process chamber 3. A gas delivery port 32 is formed in this chamber flange 34. The edge of the bottom opening of the cavity resonator 2 is joined onto the chamber flange 34. A vacuum seal is achieved by establishing a seal 9, such as an 0-ring in the joint between the two parts.
The dielectric plate 41 is held around the edge by a metal flange 42. The metal flange 42 and the dielectric plate 41 are joined by soldering in an air-tight manner. A clearance is formed circumferentially between the chamber flange 34 and the metal flange 42. This clearance forms a gas channel for the gas which is delivered from the gas delivery port 32. The gas which has been delivered from the gas delivery port 32 enters the abovementioned clearance and is diffused circumferentially.
A gas diffusing plate 50 is established on the lower side of the dielectric plate 41. The gas diffusing plate 50 is hollow inside and has a plurality of gas discharge holes, not shown in the drawing, established uniformly so as to front onto the space inside the process chamber 3. The gas which has diffused circumferentially in the abovementioned clearance is blown into the process chamber 3 via the inside of the gas diffusing plate 50.
A metal plated film 21 is coated on the surface of the process chamber 3 side surface of the dielectric plate 41. This metal plated film 21 is patterned in the form of slits of length greater than half the wavelength of 2.45 GHz microwaves. The microwaves which resonate inside the cavity resonator 2 pass through the metal plated film 21 and radiate into the process chamber 3, and then plasma is generated in the gas atmosphere within the process chamber 3.